Rorke Data Galaxy Aurora LS Series Configuration And Setup page 79

G A L A X Y ® A U R O U R A L S C O N F I G U R A T I O N A N D S Y S T E M I N T E G R A T I O N G U I D E
Air Intakes/Exhaust: These should be periodically cleaned, as their blockage could generate
unnecessary heat inside the array.
Rack Mounting: On many of the chassis we've used, there are problems associated with the
weight of the unit when used in a Rack configuration. The rack mounting system typically
starts at the chassis itself, with a series of tangs which are punched out of the metal. In a lot of
cases, these can become bent, making it difficult to attach the rails – you can bend the tangs
out, but it should only be by enough to get the rail on – overbending it will cause the rail to jam
when the unit is rack-mounted. The slides which attach to the sides have to go on particular
sides and with a particular orientation. Currently, on chassis we've used, it isn't possible to
install the slides with an incorrect orientation unless they are on the wrong sides. On the front
of the chassis are a pair of rack ears. These ears are held to the chassis using screws which
go into the chassis by an amount less than 1/16", and are not made to take any weight
whatsoever.
MTP: The left ear on most chassis, also contains electrical connections between an MTP
(Map ping/Test Panel) on the ear, which turns on or resets the power, and provides LED status
information, and connects to the motherboard. On the front of the ear is a handle – most are
connected with sub-standard screws which only extend into the handle by 1/8" – again, these
can not take any weight. The MTP electrical connection is much more complex than it looks.
Inside the rack ear is a small circuit board – on this board is a connector which is attached to a
flat ribbon cable. The connector can be opened and ribbon cable removed, but it is very
difficult to reassemble. The ribbon cable passes through a hole in the chassis (and can be
easily damaged by metal cutting into the cable), to another circuit board inside the chassis.
This inner circuit board also has a connector for the ribbon cable which can be opened/closed,
then it is attached to another removable cable which goes to the MTP connector on the
motherboard. The desktop chassis also contains an MTP, but is it not as delicate, easy to
break, or as complex as the ones on the Rack enclosures.
Chassis Construction/Bulkheads/Air Baffles: Many of the chassis used aren't just a simple
piece of metal bent into the shape of a PC. The rack-mount chassis, for example, are no less
than 3 layers of metal at almost any given spot at the front, 2 at the bottom where the
motherboard is, and sometimes 2 at the rear. It is possible to disassemble these layers,
however the correct tools and replacement parts must be used. Most chassis have an inner
bulkhead, separating the front of the chassis from the rear of the chassis, typically holding the
central fans. The bulkhead is removable to allow easier access to many of the components.
Finally Air Baffles: These provide directed cooling at specific components, and some provide
protection for more delicate internal components. On some of the rack chassis, there is an air
baffle covering the DC power distribution board. This is strictly to provide airflow while
protecting the delicate components on that board. It can be removed if necessary, but should
be replaced when done. Finally, there is usually a main air baffle in the system, directing air
from the fans across the CPU and RAM. If the system has a Nehalem 900-series CPU, it isn't
currently possible to use the air baffle, because the CPU fan required by Intel is too tall.
Mounting Hardware: While it is not likely that a piece of mounting hardware will fail in the
field, one problem was discovered when developing prototypes: Not all motherboard standoff
positions are used in the chassis for any given particular motherboard. If a standoff is placed
in a position where there is no corresponding hole in the motherboard, it can short part of the
motherboard to ground which wasn't intended, leading to possible damage or a blank screen
on bootup.
Environment/Care: Environment can play a large factor in the lifespan of the array. The two
harshest environments are near beaches, and in climates with high humidity. Rust forms as
the result of a chemical reaction, where electrons leech out of the iron in the chassis, into the
surrounding oxygen. Water and salt accelerate this reaction because they contain minute
traces of electrolytes. Rust can be removed via the use of Royal Naval Jelly. But bear in mind,
78 Section 4 Troubleshooting Guide